These data represent monthly averaged values of selected variables for the Data Distribution Centre (DDC) of the Intergovernmental Panel on Climate Change (IPCC). (see also https://www.ipcc-data.org/) The model output prepared for IPCC Fourth Assessment climate of the 1%year CO2 increase experiment (to doubling). This simulation depends on 1%/year co2 increase to 70 years to CO2 doubling, then continues to 150 years, data were output starting with nominal data of January 1980. For this experiment there is 1 ensemble run available. Model output data for CMIP3 in higher temporal resolutions and further variables are available in ESGF at https://esgf-node.llnl.gov/search/cmip3/.